Electric switch sensitive to small operating movements



A. ARNOT 2,408,901

ELECTRIC SWITCH SENSI'I'IVE TO S MALL OPERATING MOVEMENTS Oct. 8, 1946'.

Filed April 30. 1943 1 a. i :EIEit Patented Gct. 8, 1946 ELECTREC SWITCHSENSITIVETO- SMALL OPERATING MOVEMENTS Alf-red Arnot', Warrington,England, assignor to Aeronautical & Mechanical Investments Limited; aBritish company Application April 30, 1943, Serial No. 485,220 In GreatBritain April 23, 1942 2 Glaims.

This invention comprises improvements in or relating to electricswitches sensitive to small operating movements.

It is an object of this invention to provide an electrical switchmechanism which is sensitive to very small movements of the operatingmember. For example in the mechanism described in patent application No;469,270, which comprises an electrical device for transmitting movementfrom a transmitter to a receiver such a switch mechanism is called for,and maybe necessary both at the transmitter and at the receiver.

According to the present invention anelectric switch mechanism comprisesin combination a base, a contact-carrier pivotally mounted on the baseand having a pallet-face in a plane to one side of the pivotal axis andfacing away therefrom, a switch contact-member operatively connected tothe contact-carrier so as to be operated when the contact-carrierrotates about its aXis, and an actuating-member having a palletengagingportion which is mounted so as to be yieldingly pressed on the palletface and to be so movable that the line of pressure can be shifted toone side of the contact-carrier pivot to actuate the contact-member inone direction, and to be returned to return the contact-member Theactuating-member may be capable of being centered so that its-line ofpressure passes through the pivot axis and of being moved to either sideto move the contact-member correspondingly, and the contact-member mayengage two contacts, one when moved to one side and the other when movedto the other. Thus it is possible to make the switch member operate as atwo-way switch with a neutral or off position in the centre, if desired,although it is within the scope of the invention to use the switchmember for closing a single contact only.

Preferably the contact-carrier is further controlled by a spring mountedon the base in such a position as to act as a toggle-spring and thus toincrease the certainty of movement of the contact-member intocontact-engaging position.

The following is a description, by way of example, of one constructionof switch mechanism in accordance with the invention:

In the accompanying drawing,

Figure 1 is a front elevation of an electric switch mechanism accordingto this invention;

Figure 2 is a plan;

Figure 3 is a diagrammatic perspective view of the switch mechanism andof one possible arrangement of parts and connections for automaticservo-operation.

The switch mechanism comprises an operating spindle II which isrotatably mounted and carries at one end a head l2 containing atransverse spring plunger [8 which constitutes a switch-actuatingmember, projects from one side of thehead and has a knife edge i l, theline of which extends in a direction parallel with the aXis of theoperating spindle ll. Concentric with the spindle H and surrounding it,but mounted-for independent rotation, is a circular switch base l5- ofmetal and on the switch base there is pivotedon a post l6, close to thespring plunger l3, acontact-carrier H in the form ofan oblong block ofmetal having a pallet face 18 which engagesthe knife edge 14 on thespring plunger I3; Thepallet-iace 18 in its neutral position is atrightanglesto the line-of'pressureof the-spring plunger l3, the axisofthe pivot-post IQ of the contactcarrier being in this positionintersected bythe line of pressure ofthe-spring plunger it through theknife edge M. The contact-carrier has a V groove 19 cut inone end and onthe rotatable switch base there is an upstanding block 28 having anotherV groove 2 l which faces the V groove: H! in the contact-carrier.Between the two V- grooves there extends a piece of flat-section:spring-steel 22 which is of curved or sinuous formation so that itconstitutes a somewhat stiff compression spring, and thelocation of theparts is such that when the contact-carrier H is in its mid positionwith the line of pressure of. the spring plunger 13 intersecting theaxis N3 of the pivot the spring 22 which extends between the V grooveshas a line of pressure which also intersects the axis it of the pivot.The spring 22 is thus a toggle spring, and while it does not prevent thespring plunger l3 from holding the contactcarrier ll at rest in itscentral or normal position, it assists in pushing the contact-carrierover to one or other of its extreme positions immediately the springplunger of the operating member is moved so that it presses either toone side or to the other of the aXis of the contact-carrier IT.

From the other end of the contact-carrier I! there extends a springarm23 which constitutes a contact-member and terminates in a doublesidedcontact 24. The contact 24 plays between two fixed insulated contactposts 25, 26 on the switch base. A bridge-piece 21 carries a bearing forthe end of spindle ll.

Therefore if the parts are in their normal position the axis of thespring plunger l3 of the operating spindle will intersect the pivot l6of the contact-carrier H and the switch contact 24 will be heldcentrally between the two fixed contacts 25, 26, without touching eitherof them. A very small angular deflection of the operating spindle I I ineither direction will cause the line of pressure to be altered and theswitch contact will be brought firmly into engagement with one or theother of the contacts 25, 26 on the rotatable sWitch base. If such aswtich mechanism is employed in apparatus of the kind described in theaforesaid patent application No. 469,270 the operating spindle ll of theswitch may constitute the control shaft on the receiver, as shown inFigure 3, and the switch base I5 may be connected to a follower shaft28, by means of the bridge piece 21 or otherwise. This mechanism thustakes the place of the cam-closed switch contacts described in theaforesaid specification.

In Figure 3 the parts are similar to Figures 1 and 2 but the base 15 isshown as having gear teeth around its edge meshing with a pinion 29 on ashaft 30 of a reversible motor 3|. H is operated in either direction bymagnetic pawl-operating devices the pawls of which operate a ratchetwheel 32. The motor is connected by line 33 to a source of electricpower 34 and by lines 35, 36 to the contact posts 25, 2B. tact 24 isconnected by line 3'! to the other terminal of supply. Thus when contact24 is closed against 25 the motor 3! will operate in one direction andwhen closed against contact 26 the motor will operate in the otherdirection. The directions of movement are arranged to be such that thebase l5 always tries to follow the shaft H and thus shaft 28 ismotor-driven to the same extent of movement as shaft I l. The motor maybe such as the one described in British patent application No. 6373/ 41.

The switch may also be used in a transmitter mechanism of the kinddescribed in the alternative form of apparatus in the aforesaidspecification N 0. 469,270, where the transmitter has a control shaftcarrying spring contact arms.

In the mechanism herein described it is necessary that the springloading behind the knifeedged plunger I3 on the operating spindle IIshould be great enough to ensure that the mechanism will re-set toneutral position, that is to say with the switch contact 24 out ofengagement with either of the contacts 25, 26 on the switch base, afterit; has been displaced, when the operating spindle regains the positionin which the plunger is in line with the axis of the contactcarrier. Ifthe spring loading is sufliciently great The shaft The conthis will beattained. Stability may be further increased, at the expense ofsensitivity, by slightly flattening the knife edge.

It will be appreciated that while a rotatable actuating member androtatable switch base have been described the invention is applicable toother cases, for example where the switch base is fixed, or where onepart (such as the actuating member) moves in a straight line relativelyto the other part (such as the base) instead of being rotatably mounted.

I claim:

1. An electric switch mechanism comprising a base, a pivotedcontact-carrier mounted on the base and having a pallet-face in a planeto one side of the pivotal axis and facing away therefrom, a switchcontact-member carried by the contact-carrier so as to be operated whenthe contact-carrier rotates about its axis, an actuating member having aportion movable towards the pivot of the contact-carrier and means topress said pallet-engaging portion against the pallet-face of saidcontact-carrier, said actuating member being mounted so that its line ofpressure passes through the axes of said pivot and is capable ofmovement to either side to move the contact-carried correspondingly, apair of contacts adapted to be alternatively engaged by saidcontact-member depending on its direction of movement so that thecontact member may act as a two-Way switch member with a central neutralposition, and a spring mounted on the base and engaging thecontact-carrier in such a position as to act as a toggle-spring and thusto increase the certainty of movement of the contact-member.

2. An electric switch mechanism comprising in combination a rotatablymounted base, a contactcarrier pivoted on said base eccentrically to thecenter of rotation thereof and having a palletiace facing towards thecenter of rotation of the base, a switch contact-arm extending from saidcontact-carrier, a contact on the base engageable by said contact-arm, arotatable actuating member coaxial with the base, a pallet-engagingportion on the actuating member movable radially outward into contactwith said pallet-face, resilient means for urging the pa1let-engaginmember toward said pallet-face, and a toggle compression spring mountedon said base and engaging said contact-carrier.

ALFRED ARNOT.

